1. Field of the Invention
The present invention relates to an improved locking mechanism for restraints such as handcuffs. More specifically, the invention provides a locking mechanism having a flat spring, serving to bias the bolt against the jaw, and to resist movement of the stop when the stop is in the double locked position.
2. Description of the Related Art
Double locking restraints such as handcuffs, leg irons, and other shackles are commonly used by police to restrain those in their custody, for both the additional security that they offer, and the increased safety for the handcuffed person achieved by minimizing the likelihood that the jaw will inadvertently tighten around the person""s wrist or ankle. Single locked is defined as permitting the jaw to ratchet inward to tighten the bracelet of the handcuff, but not move outward to loosen or open the bracelet. Double locked is defined as resisting both inward, tightening, and outward, loosening, movement of the jaw. However, presently available double lock mechanisms utilize a stop that is held in place by a spring-biased tab abutting a detent within the stop. Such designs provide maximum resistance to movement of the stop immediately before movement begins, with no resistance to movement provided after the stop begins moving. Such designs may not only be picked too easily, but also the stop may slide from the double locked to the single locked position if the handcuff is subjected to a sufficiently strong blow.
Others have proposed various modifications to handcuffs in an attempt to address this and other problems. For example, U.S. Pat. No. 4,314,466, issued to J. E. Harris on Feb. 9, 1982, describes a handcuff incorporating a sliding stop for preventing the bolt from moving out of engagement with the jaw. The bolt is automatically pushed into the double locked position by a lever actuated by contact with a handcuffed person""s wrist as the handcuff is applied. When the stop is moved into the double locked position, the end of the stop closest to the pin slides into a recess, so that a ledge resists movement of the stop in the opposite direction. Unlocking the handcuff requires moving the stop so that it clears the ledge before turning the key to move the stop. Means for moving the stop away from the ledge include a second pin, a second keyhole for a second key, or a rod extending through the swivel. Turning the key in the opposite direction moves the bolt away from the jaw in the conventional manner.
U.S. Pat. No. 4,574,600, issued to W. P. Moffett on Mar. 11, 1986, describes a handcuff wherein a leaf spring biasing the bolt toward the jaw slides between a position wherein it blocks movement of the bolt, and a position wherein it permits movement of the bolt, but continues to bias the bolt toward the jaw. The spring is moved to the first position by inserting a pin on a handcuff key into the appropriate slot, and move to the second position by inserting and turning the key in the keyhole.
U.S. Pat. No. 4,694,666, issued to R. S. Bellingham, et al. on Sep. 22, 1987, describes a handcuff having a sliding runner that blocks movement of the bolt in one position, permitting movement in the other position. The handcuff is unlocked by turning the key to slide the runner out of engagement with the bolt, and continuing to turn the key in the same direction to move the bolt out of engagement with the jaw.
U.S. Pat. No. 4,697,441, issued to M. L. Allen on Oct. 6, 1987, describes a handcuff using a conventional locking mechanism, and having bracelets joined by a single pin, permitting the bracelets to pivot within the plane in which they are located with respect to each other, thereby remaining parallel both in use and in storage.
U.S. Pat. No. 5,138,852, issued to D. E. Corcoran on Aug. 18, 1992, describes a handcuff having a locking mechanism with a pair of individually spring-biased pawls combined with a slidable bolt for blocking movement of the pawls. The bolt includes a pair of detents for engaging a tab at the opposite end of each spring for the pawls. The handcuff has a cushioned edge, with the cushion capable of fitting between the side plates when not compressed, but not fitting between the side plates when compressed.
U.S. Pat. No. 5,461,890, issued to R. LeFavor on Oct. 31, 1995, describes a handcuff having a handle for controlling a handcuffed person. This patent does not describe or illustrate any double locking mechanism.
U.S. Pat. No. 5,463,884, issued to L. S. Woo et al. on Nov. 7, 1995, describes a handcuff having a quick release button. The quick release button may operate either the bolt but not the double lock, or may operate both the bolt and the double lock. In the second configuration wherein the quick release button operates both the bolt and double lock, it is removable so that the handcuff can be used for both training and for restraining those in custody. A similar handcuff is described in U.S. Pat. No. 5,743,117, issued to L. S. Woo on Apr. 28, 1998.
U.S. Pat. No. 5,555,751, issued to F. W. Strickland et al. on Sep. 17, 1996, describes a handcuff wherein each bracelet is closed by sliding a telescoping handle portion surrounding the handcuff""s locking mechanism toward that bracelet. When the handle is moved toward the bracelet, it causes a tapered cam to engage rollers on each bracelet arm, thereby pivoting the arms to their closed position. A spring-biased bolt secures the cams in their closed position. Inserting and turning a key engages the spring-biased bolt, causing the cam springs to retract the cams and open the bracelet.
U.S. Pat. No. 5,613,381, issued to J. M. Savage on Mar. 25, 1997, describes a rigid handcuff incorporating a deadbolt for engaging a waist chain, actuated by the same cam used to move the bolts out of engagement with the jaws. This patent does not illustrate or describe any double locking mechanism.
U.S. Pat. No. 5,660,064, issued to R. J. Ecker et al. on Aug. 26, 1997, describes a handcuff having a double lock bolt with two notches for receiving a spring-biased tab, with one notch corresponding to the double locked position (wherein the bolt resists movement of the ratchet arm), and the other notch corresponding to the single locked position (wherein the bolt does not resist movement of the ratchet arm).
U.S. Pat. No. 5,697,231, issued to T. H. Tobin, Jr., on Dec. 16, 1997, describes a handcuff wherein the two bracelets are joined by a swivel link having a pair of spherical lobes connected by a neck. Each spherical lobe is secured within the lock housing of one of the two bracelets.
U.S. Pat. No. 5,797,284, issued to A. E. Lurie on Aug. 25, 1998, describes a handcuff having the position of the spring-biased bolt controlled by a cylinder lock. The cylinder lock has a central position permitting ratcheting engagement of the bolt and jaw. The cylinder lock may rotate between one position wherein movement of the bolt is resisted, and a second position disengaging the bolt from the jaw.
U.S. Pat. No. 5,799,514, issued to T. H. Tobin, Jr., et al. on Sep. 1, 1998, describes a handcuff having a locking mechanism controlled by compressed gas pressure. A spring-biased bolt engages the jaw. A piston having a default central position permitting ratcheting movement of the jaw may be moved by compressed gas pressure between one position wherein all movement of the bolt is resisted, and another position disengaging the bolt from the jaw.
U.S. Pat. No. 6,311,529, issued to J. B. Kang on Nov. 6, 2001, describes a handcuff having one or two gears engaging the bracelet""s jaw, with each gear having a secondary gear engaging a pivoting, flat spring-biased ratchet arm. A sliding stop member may double lock the handcuff being moved into a position wherein it abuts the ratchet arm, resisting movement of the ratchet arm.
French Patent Application No. 2518-622-A, published Jun. 24, 1983, describes a handcuff using an arcuate ratchet biased towards its locked position by a coil spring, thereby securing the jaw. A barrel lock using a second key is used to double lock the handcuff.
Russian Patent No. 2015283-C1, published Jan. 15, 1994, describes a handcuff using a lever to engage the teeth of the jaw. An L-shaped locking bolt holds the lever in engagement with the jaw. A keyhole in the side of the lock housing permits an L-shaped key to disengage the lock.
Russian Patent No. 2005872-C1 illustrates another handcuff locking mechanism.
Accordingly, a handcuff having a double locking mechanism providing resistance to movement out of the double locked position not only at the beginning of movement, but also throughout the first portion of such movement, is desired. Additionally, a handcuff locking mechanism having a double locking mechanism dimensioned and configured so that resistance to movement of the stop increases as the stop is moved out of the double lock position is desired. Furthermore, there is a need for a handcuff having a locking mechanism that is more difficult to pick. Additionally, there is a need for a handcuff locking mechanism that will remain locked if a blow is inadvertently struck to the handcuff""s locking mechanism.
The present invention provides an improved locking mechanism for restraints, providing a decreased possibility of inadvertent unlocking of the double lock mechanism, and increased difficulty in picking the lock.
The improved locking mechanism will be utilized with restraints such as handcuffs, leg irons, or other shackles, which are typically formed having a pair of side plates on either side. The side plates enclose a locking mechanism at one end, and pivotally secure a jaw between them at their other end. It is well known that the side plates also typically secure a means for joining the shackle to another identical or substantially similar shackle between them as well, for example, a chain, a hinge, etc. The jaw typically includes a plurality of ratcheting teeth at its free end, with the ratcheting teeth facing outward, so that they are dimensioned and configured to engage the locking mechanism.
The locking mechanism includes a spring-biased bolt, having one or more teeth dimensioned and configured to engage the teeth of the jaw. The bolt includes means for restraining its movement between a locked position into which it is spring-biased, and wherein it engages the jaw, and an unlocked position, wherein it permits movement of the jaw in either direction. In the illustrated example, this means includes a pivot. The bolt also includes means for engaging the flag of a handcuff key.
The locking mechanism also includes a slidably movable stop member, which slides between a first position wherein it permits movement of the bolt between the locked and unlocked positions, and a second position wherein it resists movement of the bolt away from the locked position. The stop includes at least one detent for engaging a means for securing the stop in the double locked position. In a locking mechanism of the present invention, when the stop is in a double locked position, the same spring that biases the bolt toward its locked position will engage one of these detents, thereby securing the stop in the double locked position. The locking mechanism also includes a double lock pin, which may be pushed utilizing a post on the handcuff key to push the stop from the single locked first position to the double locked second position, and means for engaging the flag of a handcuff key so that rotating the key may move the stop from the double locked position to the single locked position.
Many of the advantages of the improved locking mechanism are provided by the configuration of the spring. A preferred spring is a flat spring having a pair of J-shaped tips, with one J-shaped tip dimensioned and configured to engage the bolt, and the second J-shaped tip dimensioned and configured to engage either the lock mechanism housing, or the detent within the stop. The spring is preferably angled at an acute angle with respect to the stop. Therefore, as the stop moves from the double locked position to the single locked position, the resistance to this movement supplied by the spring will gradually increase until a maximum level of resistance is reached, at which point the spring will disengage from the stop, permitting the stop to move the remainder of the distance to the single locked position. In presently available handcuff locking mechanisms, a spring-biased member engages a detent in the stop when the stop is in the double locked position, exiting the detent as soon as the stop begins to move away from the double locked position. Therefore, in a conventional handcuff, maximum resistance to movement of the stop is provided only at the beginning of the stop""s movement. By providing resistance to movement of the stop over a greater portion of the stop""s movement from the double lock position to the single lock position, and by making the point of maximum resistance later in that movement, the locking mechanism becomes more resistant to picking attempts and less likely to move from its double locked position when subjected to a hard blow.